1. Field of the Invention
The present invention deals with textured polyurethane molded articles having multiple sheet layers, which comprise:
a) an outer coating layer; PA1 b) a middle layer of a sheet containing urethane groups and/or urea groups prepared from a heat curable composition which is storage stable at room temperature; and PA1 c) a backing layer made from noncellular or cellula polyurethane which optionally contains an insert and/or reinforcing material. PA1 a) an outer coating layer; PA1 b) a middle layer of a sheet containing urethane and/or urea groups; and PA1 c) a backing layer made from noncellular or cellular polyurethane which optionally contains an insert and/or reinforcing material; PA1 i) an organic polyisocyanate; PA1 ii) at least one compound having two hydrogen atoms reactive to isocyanate groups and having an average molecular weight of 250 to 8500; PA1 whereby a room temperature solid organic polyisocyanate (i), in the form of distinct particles having a particle diameter of 0.1 to 150 microns, is deactivated on the particle surface by a chemical reaction with a deactivating agent so that from 0.1 to 20 equivalent percent of the total available isocyanate groups from (i) are reacted with the deactivating agent and the resulting surface modified polyisocyanate is dispersed into at least one compound having two hydrogen atoms reactive to isocyanate groups; PA1 iii) chain extending agents and/or crosslinking agents having an average molecular weight of 62 to 500 and having an average functionality of 2 to 4 and; PA1 iv) catalysts. PA1 a) an outer coating layer; PA1 b) a middle layer of a sheet containing urethane and/or urea groups; and PA1 c) a backing layer made of noncellular or cellular polyurethane which optionally contains an insert and/or reinforcing material wherein the coating layer is applied to the textured inside of a mold heated to from 60.degree. to 150.degree. C. PA1 i) an organic polyisocyanate; PA1 ii) at least one compound having two hydrogen atoms reactive to isocyanate groups and having an average molecular weight of 250 to 8500; PA1 whereby a room temperature solid organic polyisocyanate (i), in the form of distinct particles having a particle diameter or 0.I to 150 microns, is deactivated on the particle surface by a chemical reaction with a deactivating agent so that from 0.1 to 20 equivalent percent of the total available isocyanate groups from (i) are reacted with the deactivating agent and the resulting surface modified polyisocyanate is dispersed into at least one compound having two hydrogen atoms reactive to isocyanate groups; PA1 iii) chain extending agents and/or crosslinking agents having an average molecular weight of 62 to 500 and having an average functionality of 2 to 4 and; PA1 iv) catalysts.
2. Description of Related Art
The preparation of molded foam from polyisocyanate addition polymerization products, for example, from hot or cold molded, or integral skin foams is the subject of numerous patents and publications. Specific examples are: Advances in Urethane Science and Technology, Vol. 1 through 8, K. C. Frisch et al, Technomic Publishing Company, Inc., 1971 through 1981; the Monograph of J. H. Saunders and K. C. Frisch High Polymers, Vol. XVI, Polyurethanes parts 1 and 2, Verlag Interscience Publishers, 1962 and 1964; or Integral Skin Foams by H. Piechota and H. Roehr, Carl Hanser-Verlag, Munich and Vienna, 1975.
If the molded articles made from integral skin foams are not used as, for example, construction elements in the interior of motor vehicles, then the molded foams must be provided with a decorative surface, for example, woven material from plastic or natural fibers or thermoplastic films. The decorative layer can be bonded, for example, with a core layer. Following another process technology, preformed covering materials can be foamed in place. There are basically two methods available for achieving this. Gas impervious covering materials or films are deep drawn in closed molds; or single component or dual component coatings are injected into the mold according to the in mold coating process. After either processing variation, the covering material or the coating layer is subsequently foamed in place (Plastics Handbook, Vol. 7 "Polyurethanes", second edition 1983 edited by G. Oertel, Carl Hanser-Verlag, Munich and Vienna).
Typical predominantly used covering materials are polyvinyl chloride (PVC) films or PVC/acrylonitrile-butadiene-styrene (ABS) copolymer films. However, such plastic films have many disadvantages. For achieving the required product applications, material properties such as for example, tear propagation strength, tear elongation, or the correct feel, the PVC or PVC/ABS films generally must be modified by adding plasticizers such as for example, phthalic acid esters. For assuring the necessary thermal stability of approximately 130.degree. C., the aforesaid films must be equipped with heavy metal stabilizers. The plasticizers used either contain, or after curing form volatile constituents which lead to the undesired formation of a coating, particularly on windows, for example the so-called fogging.
As the plasticizer bleeds out over the course of time, the films become rigid, brittle and cracked. Another serious disadvantage is based on the mutual negative influence of PVC and/or PVC/ABS films with poured in place polyurethanes; particularly if the polyurethane foams are prepared in the presence of conventional amine catalysts which results in the rapid embrittlement of the decorative layer. In addition, a problem is the recycling of PVC waste and the formation of HCl in fires.
Numerous experiments were aimed at replacing PVC or PVC/ABS films by other suitable materials such as, for example, films of thermoplastic polyurethanes (TPU). Since TPU films after deep drawing exhibit the so-called memory effect, i.e. in deep drawing the desired, needled upper surface structure is lost, their use did not lead to the desired success. Textured polyurethane films such as for instrument panels, indeed can be manufactured from TPU powder employing a powder sintering process. However, since this method necessitates a significant energy requirement, it is unprofitable and normally only leads to certain light fast polyurethane films.
Textured polyurethane films prepared according to the dual component thermosetting process overcome this disadvantage as seen in Kunststoffberater 32, pages 27 through 28, October, 1987, Booklet 10. With the help of this process, molded articles can be obtained having a natural surface structure such as for example, leather grain, seams, etc. The exact proportioning of the polyol and polyisocyanate components pose difficulties in this production process since even small fluctuations in the mix ratio of the starting components lead to a sharp decline in the mechanical properties, particularly in the thermal stability of the films prepared. Moreover, preruns and postruns lead to a significant loss of material.